Billing model

The recurring invoice for a SmarterMail service is assembled dynamically each billing cycle. The module's hooks.php listens on the WHMCS InvoiceCreated event and rewrites the invoice so it reflects actual usage at the moment it is generated.

There are two billed dimensions: disk usage (the base line) and per-mailbox protocol add-ons (EAS / MAPI).

1. Disk usage — the base line

• The WHMCS cron periodically calls the module's UsageUpdate, which queries the SmarterMail API for the domain's real disk usage and stores it (in MB) in tblhosting.diskusage. (Schedule the cron daily — see Installation.)
• At invoice time the hook reads diskusage, divides by GB per billing tranche (option 1), rounds up to whole tranches, and multiplies the product's recurring price by that count.

Example — price $6.00, tranche 10 GB, customer at 21 GB:

ceil(21 / 10) = 3 tranches  →  3 × $6.00 = $18.00
Line description: "Email hosting (21.00 GB used of 30 GB billed)"

2. ActiveSync (EAS) and MAPI/Exchange — per mailbox

For each mailbox, the module knows whether EAS and/or MAPI is enabled, and adds invoice lines accordingly:

Mailbox state	Line added	Price (option)
EAS only	ActiveSync (EAS): bob@domain.com	option 2 (2.00)
MAPI only	MAPI/Exchange: bob@domain.com	option 3 (3.00)
EAS + MAPI	EAS + MAPI/Exchange: bob@domain.com	option 4 combined (4.50) — replaces the two separate lines

• A price of 0 (option 2/3) disables billing for that protocol — it can still be offered for free.
• The combined rate (option 4) is a discount, not a sum: a both-enabled mailbox bills 4.50, not 2.00 + 3.00. Set option 4 to 0 to bill the two separate lines even when combined.

3. The activation threshold (option 16)

By default a protocol must have been enabled for ≥ 1 cumulative day within the period before it is billed. This avoids charging for brief trials and is idempotent (billed once per period regardless of how many times it's toggled).

Key behaviours:

• Cumulative, not continuous — 12 h + 12 h across the period counts as 1 day.
• Deleted mailboxes that crossed the threshold are still billed on the next invoice, with the active date range ("Active from DD-MMM to DD-MMM") — so the charge can't be dodged by deleting the mailbox before invoicing.
• 0 = live billing — bills whatever is enabled at the exact moment the invoice is generated, with no minimum.

See Product configuration → EAS / MAPI billing threshold for the full implications.

Setting the price

The per-tranche price is the product's normal recurring price (Products/Services → Pricing tab). Everything on the Module Settings tab (options 1–4) only sets how that price is multiplied and the add-on rates — see Product configuration → Billing.

Tip: because the base line is rewritten to "N tranches", set the product's Pricing to the price of one tranche, not the expected total.